Purple Apatite on Siderite

Calcium Phosphate Fluoride Hydroxide Chloride, Ca5(PO4)3(F,OH,Cl)
Crystal System: Hexagonal
Hardness: 5.0
Density: 3.16-3.22

Apatite is a group name, applied to phosphates, arsenates and vanadates. It's members are the most common of the phosphorus-bearing minerals. The group members are differentiated on the basis of their predominant anions i.e. fluorapatite (FL), hydroxylapatite (OH), or chloroapatite (CL). Apatites are formed under a variety of conditions but most commonly occur as accessory minerals in igneous rocks. They also occur in marine sedimentary rocks formed by chemical deposition, in fossils, and in metamorphic rocks.

Apatites vary widely in color from colorless to yellow, green, brown, red, blue and purple. Some apatites display a yellow fluorescence under ultraviolet light. Group members exhibit hexagonal, prismatic crystals which may be stubby to elongated and are often terminated by dipyramidal faces.

Stuart provides the following remarks:

"This sharp gemmy crystal of rich color shows off the very best of Panasqueira Apatite. The purple crystals are the rarest and most desirable. These are probably only surpassed by one locality in Maine which produced the finest known Purple Apatite now in the USNM known as the "Roebling Apatite."

Iron Carbonate, FeCO3

Siderite is a member of the calcite group that commonly occurs both in bedded sedimentary rocks, and as a hydrothermal vein mineral.

Rocks from Stuart Wilensky's Collection

Index of Specimen Images

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bkeller@rockhounds.com 8/5/95